1. Field of the Invention
The present invention relates generally to mobile CB transceiver systems and, more particularly, to an improved mobile CB transceiver system having the circuitry partitioned such that the receiver, transmitter and frequency synthesizer circuits may be located in a remote position while the control circuitry is housed in a readily accessible combination transducer and control unit.
2. Description of the Prior Art
Many conventional radio receivers are provided with a microphone and the circuitry necessary to transmit or broadcast a radio signal modulated with audio frequency information, usually in the form of human speech, and such radios are usually referred to as "citizens band", "CB" or "two-way radios" or, more generically, "transceivers". For a number of years, such transceivers have been available in motor vehicles to enable the driver of the vehicle, while driving, to communicate with a person having a similar transceiver either at a stationary location or in another vehicle for information, entertainment or emergency purposes.
Recently, the use of mobile transceivers has gained in popularity to a point where a large percentage of both cars and trucks on the road today are equipped with CB radios which are usually purchased separately and installed adjacent to or under the vehicle's dashboard and away from the steering wheel column where space is a little more plentiful and the transceiver cabinet will not significantly interfere with the driver's operation of steering, braking, accellerating or other vehicle control functions. Such a location permits the driver to hear received radio messages but, for messages he wishes to transmit, a microphone is attached to the transceiver by an electrical cord or cable of suitable length and the driver will normally steer the vehicle with one hand while he holds the microphone close to his mouth with the other hand so that he can transmit messages.
As the popularity of CB radios increased, concern over the likelihood that a bulky transceiver chassis mounted adjacent the dashboard could cause injury to the occupants of the vehicle in the event of an accident or sudden stop grew. Another potential safety hazard exists where the control dials for channel selection, volume control, squelch and the like are located on the transceiver unit itself since the operator, in attempting to adjust transmission and/or reception or change channels would be forced to reach over to the installed location, possibly taking his eyes off the road and causing an accident, or the like. Therefore, it has become even more essential to locate all possible controls for channel selection, transmit/receive, volume control, squelch control, and the like, within easy reach of the operator to avoid the occasions or near occasions of such accidents. This development evolved into the modern attempts to make a commercially feasible "controls in the microphone" control unit such as that illustrated in U.S. Pat. No. 4,032,844 wherein at least some of the controls were located in the mike.
Furthermore, as the market for CB radios increased, the likelihood of theft of a CB transceiver from an unattended vehicle greatly increased causing an increase in the economic loss to the vehicle owner due to either damage to the vehicle caused by forcible entry for the purpose of stealing the radio or simply due to the loss of the radio itself. Therefore, the need to disguise or hide as much of the CB radio as possible evolved as did the need for locating the main chassis where it would not be likely to cause harm or injury to the occupants of the vehicle in the event of an accident or the like.
However, prior art systems are significantly hindered by the type and number of controls actually located in the combination microphone, speaker and control unit due to the large number of electrical cables or other interconnections required between the control unit and the receiver circuitry, transmitter circuitry, and frequency synthesizer circuitry located on a remotely positioned chassis, particularly since the advent of forty-channel CB radios.
Prior attempts at arriving at an optimal partitioning of the circuitry between the remotely located chassis and the control microphone have been relatively unsuccessful. In some attempts, channel selection data was entered by dialing or otherwise selecting the channel by means actually located on the remote chassis thereby defeating the main purpose of the controls-in-the-mike concept or else the channel selection was made at the microphone and transmitted to the remotely located frequency synthesizer circuit by parallel data transmission techniques which required a costly, cumbersome and relatively complex network of many electrical cables or interconnections therebetween.
Thus, a relatively simple, inexpensive, trouble-free system was required wherein the microphone control unit combination could be quickly and easily installed and removed and the chassis containing the frequency synthesizer, receiver circuitry and transmitter circuitry could be hidden in a remote location so that no trace of the CB radio could be seen with the antenna removed or withdrawn thereby reducing the danger of theft and minimizing the danger due to accidents or the like. The present invention provides such a system and employs programmable memory means in the microphone control unit addressable by manually operable channel selection means and uses the serial transmission of channel selection data to the remotely located frequency synthesizer circuit for minimizing the number of electrical connections therebetween thereby solving or at least minimizing nearly all of the problems of the prior art systems.